Clutch release for portable power driven rotary tools



Nov. 17, 1931.

T. w. HOLLAND CLUTCH RELEASE FOR PORTABLE POWER DRIVEN ROTARY TOOLS Filed Jan. 29. 1930 Patented Nov. 17, 1931 NITED STATES PATENT OFFICE THOMAS W. HOLLAND, OF TOWSON -HEIGHTS, MARYLAND, ASSIGNOR TO THE BLACK & DECKER MANUFACTURING COMPANY, OF TOWSON, MARYLAND, A CORPORATION 01 MARYLAND CLUTCH RELEASE FOR PORTABLE POWER DRIVEN ROTARY TOOIIQ Application filed January 29, 1980. Serial No. 424,286.

Screw driving and nut running machines of the portable power driven type, having a normally released jaw clutch adapted to be 4 thrown into engagement by the pressure of '5 the operator on the tool when the bit is brought into contact with the work, are well known, one of the earliest of this kind being described in United States patent to Walter Stump, No. 1,528,584. These jaw clutch teeth have inclined engaging surfaces which give them a constant tendency to release, and the torque of the tool within the power of the motor is determined by the pressure applied by the operator to the tool to hold the jaws in engagement and to hold the bit in operative relation to and with the work. Under these circumstances, to avoid twisting off the heads of the bolts and damaging the screws,

it is necessary for the workman operating an tie-tool to exercise the maximum of care and 5 ill.

The object of the invention is to provide an adjustable release so that once the tool is adjusted tothe work the clutch is automatically released at a predetermined torque and the danger of defacing or destroying the screws, nuts and bolts in this way is eliminated.

, Several devices bearing a general resemblance to applicants construction have been 'designed and placed on the market. Some of these are of the friction type which do not transmit the full torque of the motor to the work as they commence to slip as the load increases and are gradually released during the entire operation. Others are released merely to permit the screw driver bit or socket wrench to be turned while the power is off to permit them to be brought into engagement with the screw slot or with the nut which is to be set. i

The invention in its preferred form is applied to a portable power driven screw driver or wrench otherwise known as a nut running machine. trated will be specifically described though other details may obviously be substituted for those shown. The drawings show a normally released jaw clutch with inclined engaging surfaces, the jaws being held apart For convenience, the form illus-- by a spring, the tension of which is overcome permitting the jaws to engage to rotate the spindle when the tool is pressed into operative engagement with the work, To provide for an automatic release at a predetermined adjustable maximum torque, one set of said jaws is mounted to yield without regard to the pressure applied to the tool in forcing it against the work, the point at which this jaw yields tending to release the spindle, being in the preferred form of tool. adjust able to give a predetermined maximum torque.

In the accompanying drawings I have illustrated so much of a portable power driven screw driver or nut running machine to which the invention is applied as is considered necessary to a full understanding of the manner of constructing, applying, oper ating and using the same. In the drawings: Figure 1 is a side elevation of a portable power driven screw driver or wrench to which the invention is applied, the gears and parts surrounding the spindle and a' portion of the spindle being shown in section on the plane of the spindle axis.

Figure 2 is a horizontal section on the line 2-2 of Figure 1, looking downwardly at the jaws of the lower clutch member.

Figure 3 is an elevation of the lower portion of the gear casing and spindle.

, Figure 4: is an elevation of the tool. Referring to the drawings by numerals, each of which is used to indicate the same or similar parts in the different figures, the construction shown comprises a motor housing 1, to which is secured a gear casing 2 in which is mounted a hollow driving spindle 3 and a driven spindle 4, the latter carrying at its lower end a tool chuck 5 in and to which may be secured any suitable screw driver bit, socket wrench, or the like.

More specifically descr bed, the disclosure includes a motor 10 from which the motor shaft 11 projects downwardly into the gear casing, being provided at its lower end with suitable drive pinion 12 formed on or secured to the lower end of the motor shaft. This pinion meshes with a toothed gear 14, having a downwardly rojecting hub, which is provided with teetii forming a pinion 15. This pinion (which may be secured to gear 14 in any suitable manner) meshes with a gear 16 mounted on and secured to the hollow driving spindle. 3 by which gear 16 the hollow driving spindle 3 is driven in rotation. This spindle runs in suitable bearings 18 in the casing,,and the upper end of the driven spindle 4 indicated by reference character 19 runs and slides in the bore 20 in driving spindle 3, which bore is concentric with the common axis of both spindles. The upper end of the driven spindle 4 is hollowed out at 21 to receive and contain the clutch spring 22 which holds the clutch normally released. This spring is shown in the form of a coil spring which is guided by a central pin 24 which extends through about three quarters of the coil. The lower end of the spring bears against the bottom of the hollow 21, the upper end of the pin being provided with a rounded head or button 25 against the bottom side of which the upper end of the spring bears. The button rocks on the top wall 26 of a suitable spring socket 27 in the casing 1, which spring socket is aligned with the axis of the spindles. The spring 22 is shown in expanded position in which the driven spindle 4 is depressed to its lowest position. In this position the jaw clutch which is now to be described is released.

The jaw clutch 30 comprises upper drivingclutch teeth 31 formed in the present instance on the lower surface of an enlarged portion 32 of the hollow spindle 3 whereby the teeth may be spaced outwardly from the center. The lower clutch teeth 33, which cooperate with the upper or drive teeth 31, are formed on the upper surface of a driven clutch member 34, which is keyed to the driven spindle 4 in any suitable manner as by means of ball keys 35 seated partly in slots 36' in the spindle and partly in registering slots 37 in the clutch member 34 whereby the clutch member 34 is permitted to move upwardly and downwardly relatively to the driven spindle 4 with which it rotates. The normal position of the lower clutch member 34 is controlled by a second coil spring referred to as the release spring 38, encircling the spindle and sleeve 41 thereon. This spring bears at its lower end against a nut 39 which is adjustable up and down the spindle by means of a thread 40 with which it engages, which thread is formed on the sleeve 41, mounted on and secured to the lower end of the spindle. The nut 39 is in turn held in position by means of a set screw 43 which is locked in any suitable manner as by means of a spring ring 44 seated in a groove in the nutand adapted to engage the screw slot. The spring 38 in turn bears at its upper end against an abutment 45 carried by a sleeve 46, which slides in the spindle bearing and at its upper end rests against the clutch member 34.

' The sleeve 46 rotates with the spindle 4 in ball bearings 47 and the clutch member 34 is supported in its lowermost position by the fiat abutment ring 48 which rests on the top edge of the outer ring 49 of the ball bearing 47. This bearing is seated in the gear casing, and in the form of the invention shown the hollow drive spindle 3 and the drive spindle gear 16 are supported by a spacing ring 50 which bears at its lower end on the top of the flat ring 48 and at its upper end on the bottom face of the gear 16.

The parts are illustrated in Figure 1, in the inoperative position in which the clutch jaws are disengaged and spaced apart in a vertical direction, the spindle which is supported on the lower clutch member 34 by means of a projecting shoulder 51 being in its lowermost position in which it is held by the clutch spring 22.

In the operation of the machine when the parts are in the inoperative relation illustrated in Figure 1, if the bit, screw driver or socket wrench or the like be applied to the Work and pressure applied to the tool suflicient to compress the spring 22 and permit the clutch teeth 31-33 to engage, the driven spindle 4 will be rotated by the torque of the motor transmitted through the gears 12, 14, 15, 16 to the hollow drive spindel 3 and hence through the clutch teeth to the driven spindle 4. WVhen and if the torque applied by the spindle 4 and the bit to the work exceeds that intended, to which it is assumed the spring 38 has been adjusted by means of the nut 39, the spring 38 will yield downwardly permitting the inclined teeth 33 to pass and escape or otherwise to ratchet over the teeth 31 and release the torqne, warning the operator by the noise incident to the ratcheting action of the teeth of the fact that the clutch is thus disengaged and the tool rendered inoperative for further setting of the nut or screw, etc.

In this way the tendency to injure the tool or the parts thereof, particularly the keys, gear teeth, etc., is eliminated and the tendency to twist off the heads of the bolts or to strip the threads or deface screws being driven is avoided, the torque being thus regulated and adjusted to exactly the predetermined point of release without regard to the pressure applied to the tool by the operator tending to hold the clutch members in engagement.

The ratcheting action of the teeth referred to above if continued, which is dependent upon the will of the operator, the noise of the ratcheting of the teeth giving due warning of the fact that the clutch has been released, has the effect of applying to the work tangential or circumferential blows which serve to set the screw or nut to a considerably greater extent than it can be set by the torque of the tool prior to release. It will be understood that these blows due to the passing of the teeth one over the other, are repeated with high frequency and continued so long as the tool is held in contact with the work. The

force of the blows is. however, definitely limited by the adjustable release already discussed so that the efiect obtainable in this way is definitely limited by the adjustment, as is the maximum torque of the tool and for the same purpose and with similar results.

I have thus described specifically and in detail a manually portable power driven nut running and screw driving machine embodying the features of my invention in the preferred form in order that the nature, manner of applying and using the invention maybe fully understood, however, the specific terms. herein are used descriptively rather than in a" limiting sense, the scope of the invention being defined in the claims.

What I claim as new and desire to secure by Letters Patent is:

I 1. A portable power driven tool of the screw driver and wrench type having a jaw clutch comprising two clutch members having teeth with inclined contacting surfaces whereby the torque of the tool tends to throw the clutch members out of engagement, a short hollow driving spindle on which one clutch member is carried, a toothed gear mounted on said hollow spindle immediately adjacent said clutch member, a driven spindle mounted to slide and rotate in said hollow spindle the driven spindle extending through the hollow spindle which terminates substantially at the upper end of the driven spindle, the latter carrying the other clutch member which is con nected thereto to rotate therewith, a short open annular antifriction bearing for the hol ow spindle immediately above said gear, and an antifriction bearing for said sliding spindle immediately below the clutch member which is carried thereby, an electric motor forenergizing the tool and a train of gears connecti g the motor shaft to said gear the driven spindle being chamberedat its upper end and having a spring in said chamber and a fixed support for said spring whereby a tendency is imparted to the driven spindle to move downwardly holding the clutch normally released.

2. A portable power driven tool of the screw driver and wrench type having a jaw clutch comprising two clutch members having teeth with inclined contacting surfaces whereby the torque of the tool tends to throw the clutch members out of engagement, a short hollow driving spindle on which one clutch member is formed, a toothed gear mounted on said hollow spindle immediately adiacent said clutch member, a driven spindle mounted to slide and rotate in said hollow spindle the driven spindle extending through the hollow spindle which terminates substantially at the upper end of the driven spindle, the latter carrying the other clutch member connected thereto to rotate therewith, a short open annular antifriction bearing for the hollow spindle immediately above said gear and a short antifric'tion bearing for said sliding spindle immediately below the clutch memher which is carried thereby, an electric motor for energizing the tool and a train of gears connecting the motor shaft to said gear the driven spindle being chambered at its upper end and a spring in the chambered portion bearing against a fixed portion of the tool and tending to move the spindle downwardly holding the clutch normally released, the second mentioned clutch member bein mounted to slide on the sliding spindle and a spring supporting it in operative relation to the first mentioned clutch member.

Signed by me at Towson, Baltimore County, Maryland, this 23rd day of January,

/ THOMAS W. HOLLAND. 

